(1) Field of the Invention
The present invention is for providing a communication apparatus, an information sharing system and an information sharing method for exchanging information between a plurality of communication apparatuses that are connected with a network such as a general public phone, the Internet, a Digital Subscriber Line (DSL) and an exclusive line.
(2) Description of the Related Art
Today, various kinds of communication providers provide general consumers or company users with various communication services. As one of these communication services, a voice conference service may be used for conducting a simultaneous conversation by connecting a general telephone, a cellular phone and a personal handyphone system (PHS) that are located in different places from one another. Other services include text conference services or text chat type services where a lot of users share information of data systems such as characters, images and music on the Web as the internet market becomes popular.
The above-mentioned conference system is one of a computer system or an information sharing system that includes a group of a plurality of terminal devices that are connected to each other via the network. In this information sharing system, data that corresponds to a program and the program that is stored in each terminal device is regarded as common data in a group. The system is operated in a way that this common data becomes the latest one in all the terminal devices in the group. In this case, for example, a server device is installed in the group, and this server device tries to maintain consistency of common data by broadcasting update information of the common data that is generated in each terminal device in the group to all the terminal devices in the group.
By the way, as a terminal device in the group may be switched frequently because of halfway participations or halfway withdrawals, in the case where the information sharing system executes an application for many participants, the processing workload in the server device becomes extremely high when trying to maintain the latest status of the common data in each terminal device. Therefore, it becomes difficult to realize an information sharing system economically because this information sharing system requires a high-performance server device.
Therefore, the conventional information sharing system decides one of terminal devices in a plurality of terminal devices according to the predetermination method and regards the decided terminal device as the broadcasting terminal device. The broadcasting terminal device is a terminal device for broadcasting update information concerning the update of the common data to each terminal device in the group (broadcasting terminal deciding process). Next, the information sharing system makes each of the terminal devices send the update information to the broadcasting terminal device that is determined in the broadcasting terminal deciding processing (sending processing). The broadcasting terminal device broadcasts the update information to the terminal device (broadcasting processing). Each of the terminal devices that receive the broadcasted update information updates the common data by the received update information (update processing). In this way, the consistency of the common data that is stored in each terminal device is realized by reducing the processing workload in each terminal device.
FIG. 1 is an illustration of a conventional information sharing system. For example, in the case where the terminal device A is a sending terminal device as shown in FIG. 1, update data A of the common data A is broadcast to the terminal device B, C and D. In the case where the terminal device B is a sending terminal device, update data B of the common data B is broadcast to the terminal devices A, C and D. [Patent Literature 1] Japanese Laid-Open Patent application No. 2001-331469 (the first—page 25, the second figure)
However, in the conventional art, a broadcasting terminal device is uniquely determined every time the data is updated based on the predetermined algorithm and the update data of the common data is sent from the determined broadcasting terminal device to each terminal. Therefore, even in the case where there is an judgment concerning whether the common data is updated using the update data, the receiver side of the update data can only receive the update data because the judgment cannot be reflected. No considerable problem occurs in the case where the terminal devices that form the information sharing system are, for example, a personal computer including a hard disc with a large capacity and a high-speed CPU. However, in the case where the information sharing system includes a terminal device such as a mobile phone which does not contain enough resources, it causes a shortage in a memory region for storing data which is important to the user.
An object of the present invention, even in the case where there is update data, is to provide users with an information sharing system capable of updating the common data and a communication apparatus that forms the information sharing system by reflecting the judgment of each terminal side user who received this common data.